Chapter 19

Question 1

How do all organisms depend on Sunlight?

Answer 1

The sun is the principal source of energy input to biological systems.
- All food chains start with producers, which make their nutrients from ENERGY IN SUNLIGHT.
- In this way, we all get indirect sources of sunlight through our food.

Question 2

What is a Producer?

Answer 2

It is an organism that makes its own organic nutrients using energy from sunlight, through photosynthesis.

Question 3

What is a Consumer?

Answer 3

It is an organism that gets energy by feeding on other organisms.

Question 4

What is a Herbivore?

Answer 4

A herbivore is an animal that gets energy by eating PLANTS.

Question 5

What is a Carnivore?

Answer 5

A carnivore is an animal that gets energy by eating OTHER ANIMALS.

Question 6

What is a Decomposer?

Answer 6

A decomposer is an organism that gets energy from dead or waste organic material.

Question 7

What are the types of Consumers?

Answer 7

• Primary
• Secondary
• Tertiary
• Quaternary

Question 8

What is a food chain?

Answer 8

Is a chain that shows transfer of energy from one organism to another, beginning with a producer.

Question 9

What is a Food web?

Answer 9

A food web, is a network of interconnected food chains.

Question 10

What are Trophic levels?

Answer 10

A trophic level is the position of an organism in a food chain, food web or Ecological pyramid.

Question 11

What are the Trophic levels?

Answer 11

• Producers
• Primary consumers
• Secondary consumers
• Tertiary consumers
• Quaternary consumers

Question 12

Describe the impact of humans on Food webs: (Overharvesting)

Answer 12

Overharvesting causes reduction in the number of a species, causing it to become endangered or extinct.
- It disrupts food chains because those organisms that feed on those species wont have enough food to survive.

Question 13

Describe the impact of humans on Food webs: (Foreign species and pesticides)

Answer 13

Introduction of foreign species to a habitat:
- This creates a competition for resources, causing harm to existing species and thus disrupting the food chain.
- Use of pesticides and poisons accidentally released during human activity.

Question 14

What are Ecological pyramids?

Answer 14

These are graphical representations that show the feeding relationships of organisms at each tropic level.
3 Types; Numbers, Biomass, Energy

Question 15

What are Pyramids of Numbers?

Answer 15

A pyramid of numbers, shows the NUMBER of organisms in each trophic level of a food chain.
- The lower trophic level has the LARGEST box.

Question 16

What is the disadvantage of Pyramids of Numbers?

Answer 16

They do not accurately represent the amount of energy or biomass at each trophic level.
- A single large organism (like a tree) can support many small organisms (like insects), so the pyramid can look upside down.

Question 17

What are pyramids of Biomass?

Answer 17

A pyramid of Biomass, shows the TOTAL MASS of organisms in EACH TROPHIC LEVEL of a food chain.

Question 18

What is Biomass?

Answer 18

Biomass is the total DRY MASS OF ONE plant or animal species in a food chain or web.

Question 19

What is the advantage of using a Pyramid of Biomass over numbers?

Answer 19

• The advantage is that it gives a more accurate representation of the amount of living material (biomass) at each trophic level.
• It reflects the actual energy and material transfer more realistically.
  *ex: 1 tree seems little in numbers, but in biomass its 500,000g, which is a lot more accurate to look at!

Question 20

What is a pyramid of Energy?

Answer 20

A pyramid of Energy shows the FLOW OF ENERGY at each trophic level in an ecosystem.

Question 21

Explain loss of energy?

Answer 21

As we move up the trophic levels, 90% of energy is LOST each level.
- This is because the energy is used for:
- Respiration
- Movement
- Maintaining Body temperature
- Some parts of food cant be digested
* This is why there are only max 5 trophic levels, since so much energy is lost.

Question 22

Why is it more energy efficient for humans to eat crop plants rather than livestock fed on crop plants?

Answer 22

• This is because energy is lost at each trophic level (through respiration, movement, heat, and waste), so eating crop plants directly gives humans more of the original energy. - Livestock only convert a small portion of the crop’s energy into biomass that humans can eat.

Question 23

How are Pyramids of ENERGY better than Numbers and Biomass?

Answer 23

This is because they show the actual energy transfer and loss at each trophic level over time.
- They always have a proper pyramid shape.
- They provide an accurate representation of energy decrease in higher trophic levels.

Question 24

What is the Carbon cycle?

Answer 24

The carbon cycle is the cycle which shows how carbon atoms transfer between living organisms and the atmosphere.

Question 25

What processes ADD Co2 to the atmosphere?

Answer 25

- Respiration - Decomposition - Combustion

Question 26

What processes REMOVE Co2 to the atmosphere?

Answer 26

- Photosynthesis - Fossilisation (unless fossils are burnt)

Question 27

What are the steps of the Carbon cycle?

Answer 27

1) Plants take in Co2 from the atmosphere for Photosynthesis. 2) Animals consume plants, gaining the carbon. 3) By Respiration, Co2 is released back into the atmosphere. 4) Decomposition of dead organisms releases Co2 into the atmosphere. 5) Formation of fossil fuels rids carbon, trapping it in dead organisms for years 6) Combustion of fossil fuels releases CO2 once again.

Question 28

What is the effect of Deforestation on the Carbon Cycle?

Answer 28

Deforestation reduces the number of plants available, reducing Photosynthesis. - This means plants are no longer there to absorb CO2 through photosynthesis. *Deforestation occurs for land purposes. *When trees are burned MORE Co2 is released.

Question 29

What is the Nitrogen cycle?

Answer 29

It is the Cycle showing the transfer of Nitrogen between organisms and the atmosphere.

Question 30

What are process that ADD Nitrates to soil?

Answer 30

- Nitrifying bacteria - Nitrogen-fixation (nitrogen-fixing bacteria) - Lightening

Question 31

What are process that REMOVE Nitrates from the soil?

Answer 31

- Uptake by plants (amino acid synthesis) - Leaching - Denitrifying bacteria

Question 31

What is Nitrification?

Answer 31

Nitrification is the process where Ammonia is converted to Nitrites and then Nitrates by nitrifying-bacteria to make them absorbable by plants. *increases fertility of soil

Question 32

What is Nitrogen Fixation?

Answer 32

Nitrogen Fixation is the process by which Nitrogen gas is converted into Ammonia by nitrogen-fixing bacteria. - These are present in the soil, or root nodules of leguminous plants. *(due to this, these plants can thrive in soil with a scarce source of nitrates)*

Question 33

What is Nitrogen fixation (in terms of Lightening)

Answer 33

High temperatures of lightening discharge cause Nitrogen in the atmosphere to combine with Oxygen. This dissolves in rain, and is washed in soil where they form Nitrates.

Question 34

What is Leaching?

Answer 34

- Nitrates are very soluble. So Leaching is a when nitrates dissolve in rainwater, and are carried away into deeper layers of soil.

Question 35

What are Denitrifying bacteria?

Answer 35

Denitrifying bacteria get energy by breaking down Nitrates into Nitrogen gas, which escapes from soil into the atmosphere.

Question 36

What are Nitrifying bacteria?

Answer 36

Nitrifying bacteria are those bacteria that get energy from Ammonia (by excretory products or decaying organisms) , which produces Nitrates.

Question 37

What are the steps of the Nitrogen Cycle? (8 steps)

Answer 37

1) Nitrogen is present in the atmosphere 2) Nitrogen fixation occurs. Either nitrogen-fixing bacteria convert Nitrogen -> Ammonia. - Or Lightening converts Nitrogen -> Nitrates 3) Nitrification occurs, where Nitrifying bacteria convert Ammonia -> Nitrites -> Nitrates 4) Nitrates are absorbed by Plants to make amino acids and proteins. 5) plants are digested by Animals. 6) Decomposition of decaying animals converts them into Ammonium compounds in soil. 7) Nitrification occurs again, converting Ammonium -> Nitrates in soil. 8) Denitrification occurs, where denitrifying bacteria convert Nitrates -> Nitrogen gas once again.

Question 38

What is a population?

Answer 38

It is a group of organisms of one species living in the same place, at the same time.

Question 39

What is a community?

Answer 39

It is all populations of different species in an ecosystem.

Question 40

What is an Ecosystem?

Answer 40

It is a unit containing the community of organisms AND ENVIRONMENT, interacting together.

Question 41

What factors affect population rate?

Answer 41

- Food supply - Competition (water, food) - Predation (more predators than prey) - Disease (spreads fast)

Question 42

What are the phases of a Sigmoid population growth curve? (Explain)

Answer 42

There are 4 phases: 1) Lag phase :- The population grows slowly as it adapts to the environment 2) exponential/Log phase :- Population starts to grow rapidly when resources become more available. (BIRTH RATE IS FAST, death rate is low) 3) Stationary phase :- BIRTH AND DEATH RATE IS BALANCED. Population is stable and constant. 4) Death phase :- DEATH RATE IS HIGHER than birth rate, Population declines and decreases. (due to inadequate food supply, disease)